JPS6224118Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a lightweight piston for a hydraulic actuator for a disc brake.

[Prior Art] As shown in FIG. 1, a disc brake has an inverted U-shaped fixed support member 1 that straddles a brake disc 2 and is fixed to the vehicle body on one side of the brake disc 2. A pair of friction pads 9 and 10 and a caliper 3 are supported slidably in a direction perpendicular to the surface of the brake disc 2 in a large notch 20 provided at the upper center of the brake disc. The caliper 3 is integrally equipped with a hydraulic actuator having a hollow piston 5 fitted inside the cylinder 4. When pressurized fluid is supplied to the inside of the cylinder 4, the piston 5 causes the friction pad 10 to move against the brake disc. On the right side of 2, there is also a reaction force piece 6 of the caliper 3.
As a result, the friction pads 9 are pressed against the left side surface of the brake disc 2 to generate braking force. The open end of the piston 5 has a small outer diameter, and one end of the bellows-shaped dustproof boot 12 is engaged with this small diameter section 32, and the other end is engaged with an annular groove provided at the open end of the cylinder 4. be done.

Disc brakes are considerably heavier than drum brakes, which have the same braking capacity, so it is especially desirable to reduce the weight of the caliper and piston parts.

Conventionally, the pistons used in such disc brakes were made of synthetic resin and molded together with metal reinforcing members to reduce weight.
As disclosed in Japanese Patent No. 52-39072, if the metal reinforcing member covers the entire opening end of the synthetic resin piston body, the metal reinforcing member can suppress the leakage of reaction gas that occurs during resin molding. It may remain inside the synthetic resin, causing internal cracks in the product and reducing its strength.

[Problems to be solved by the invention] Therefore, the purpose of the invention is to create a desk brake fluid that completely expels the reactive gas and prevents the strength from decreasing when the piston is resin-molded together with the metal reinforcing member. An object of the present invention is to provide a piston for a pressure actuator.

[Means for Solving the Problem] In order to achieve the above object, the configuration of the present invention includes a cup-shaped synthetic resin piston body with a
In the piston of a hydraulic actuator for a disc brake, in which a metal reinforcing member covering the inner circumferential surface, outer circumferential surface, and opening end surface of the opening end is integrally coupled, the reinforcing member is formed from a metal plate having a substantially L-shaped cross section. A plurality of gas vent holes are provided in a plate surface that contacts the inner circumferential surface and the opening end surface of the piston body, and the plate surface that contacts the inner circumferential surface is provided only at the pad side end of the piston body.

[Function] Since the metal reinforcing member 40 is provided at the pad-side end of the cup-shaped synthetic resin piston body 30,
The release of reaction gas during resin molding from the central part of the piston body 30 and the end that becomes the pressure receiving surface is not hindered, and the small diameter end 32 that transmits hydraulic pressure to the pad is reinforced and protected from frictional heat. be done.

The reaction gas during resin molding at the pad side end of the piston body 30 is discharged through the gas vent hole 3 of the reinforcing member 40.
6, 37 to the outside. Gas vent hole 3
6 and 37 also serve to prevent the reinforcing member 40 from coming off from the piston body 30.

[Embodiment of the invention] As shown in FIGS. 2 and 3, the piston consists of a piston body 30 made of synthetic resin and a reinforcing member 40 formed from a metal plate. The piston body 30 is roughly cup-shaped with an inner cavity 31, and a reinforcing member 40 is bonded to the open end of the piston at the same time as resin molding. The reinforcing member 40 is formed by forming a metal plate into a substantially L-shaped cross section, and includes a plate portion 34 that covers the open end surface of the piston body 30, a cylindrical portion 33 that covers the inner circumferential surface of the inner cavity 31, and an outer circumferential surface of the small diameter portion 32. A cylindrical portion 35 that covers the cylindrical portion 35 is provided. The end edge 33a of the cylindrical portion 33 is slightly expanded radially outward and embedded into the piston body 30. Further, a groove is formed in the small diameter portion 32 between the cylindrical portion 35 and the stepped portion 38 of the piston body 30, and the above-mentioned dustproof boot 12 is locked in this groove.

The length of the cylindrical portion 33 is such that it covers the inner circumferential surface of the pad-side end (specifically, the small diameter portion 32) of the piston body. If the entire inner circumferential surface of the inner cavity 31 is covered, it will be difficult for the reaction gas to escape.

An important feature of the present invention is that by providing the reinforcing member 40 with the cylindrical parts 33 and 35, a bag-like space is formed on the plate part 34 side. The structure is such that during molding, the reaction gas generated from inside the resin escapes to the outside through the reinforcing member 40. For this reason, the plate portion 34 is provided with a number of gas vent holes 37 at predetermined intervals in the circumferential direction, and the cylindrical portion 33 is also provided with a large number of gas vent holes 36.

The reinforcing member 40 covers the end face at the open end of the small-diameter piston body 30, the inner circumferential surface of the inner cavity 31, and the outer circumferential surface of the small-diameter portion 32, and transmits the hydraulic pressure received by the piston to the friction pad. This is to reinforce the transmission part, and as shown in Fig. 4, the cylindrical part 3
3 may be made into a reverse tapered shape to further increase the biting into the piston body 30, or a tapered portion 33b may be provided between the cylindrical portion 33 and the plate portion 34 as shown in FIG. A gas vent hole 36 may be provided.

In the above, the reinforcing member 40 is formed from a metal plate of uniform thickness, but as shown in FIG. 33d, and integrally molded so that the resin of the piston body 30 bites into this recess 33d, and the inner surface of the plate part 34 and the stepped part 38 may define a groove in which a dustproof boot is attached. .

[Effects of the invention] As described above, in the present invention, when the reinforcing member 40 is disposed inside the mold and the piston body 30 is molded with synthetic resin, the reaction gas generated from inside the resin is Since it passes through the punch holes 37 and 36 to the outside, a high degree of connection with the reinforcing member 40 can be obtained, and at the same time, the strength of the piston body 30 can be maintained. If the gas vent holes 37 and 36 are not provided, there is a risk that the reaction gas will remain on the open end side of the piston body 30 surrounded by the reinforcing member 40 and become trapped inside, resulting in internal cracks in the product. Although it is hot, such problems can be solved.

Furthermore, according to the present invention, drawing of the reinforcing member by press is easier than in the conventional example listed at the beginning, and a piston that is overall lightweight and has no problems in terms of strength can be manufactured at low cost.

[Brief explanation of the drawing]

Fig. 1 is a front sectional view of a general disc brake, Fig. 2 is a front sectional view of a piston of a hydraulic actuator according to the present invention, Fig. 3 is a left side view of the same, Figs. FIG. 6 is a front sectional view of a piston according to another modified embodiment of the present invention, with the lower half thereof omitted. 30...Piston body, 31...Inner space, 32
...Small diameter part, 33...Cylindrical part, 33a...Edge,
33b... Taper part, 33d... Recess, 34...
Plate portion, 35... Cylindrical portion, 36, 37... Gas vent hole, 38... Step portion, 40... Reinforcement member.

Claims (1)

[Scope of utility model registration request] A piston for a hydraulic actuator for a disc brake, in which a metal reinforcing member covering the inner peripheral surface, outer peripheral surface, and opening end surface of the opening end is integrally connected to the opening end of a cup-shaped synthetic resin piston body, The reinforcing member is formed by forming a metal plate into a substantially L-shaped cross section, and a plurality of gas vent holes are provided in the plate surface that contacts the inner circumferential surface of the piston body and the opening end surface, and the plate surface that contacts the inner circumferential surface A piston of a hydraulic actuator for a disc brake, characterized in that it is provided only on the pad side end of the main body.